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      /* 
            async 封装的函数都是 promise
            1. 函数中不返回任何内容，默认会返回 undefined
            2. async 包装后，会变成Promise返回，值在Promise中
        */
      async function fn1() {
        return 1;
      }
      function init() {
        console.log("fn1() -----> ", fn1());
      }
      init();
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